/*
 * Copyright (c) 2016-2017, fastquery.org and/or its affiliates. All rights reserved.
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 * For more information, please see http://www.fastquery.org/.
 * 
 */

package org.fastquery.util;

import java.io.File;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URL;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

import org.fastquery.core.Repository;
import org.fastquery.core.RepositoryException;
/**
 * 
 * @author <a href="mailto:ohergal@gmail.com">ohergal</a>
 * @author xixifeng (fastquery@126.com)
 */
public class ClassUtil {	 
	
	private ClassUtil(){}
	
	/**
	 * 从包package中获取所有的Class
	 * @param packageName 包地址
	 * @param loader 类加载器
	 * @return clazz 集
	 */
	 @SuppressWarnings("unchecked")
	public static List<Class<Repository>> getClasses(String packageName,ClassLoader loader){
	     		 
	     //第一个class类的集合
	     List<Class<Repository>> classes = new ArrayList<>();
	     
		 // packageName 很可能是一个完整的类
		 try {
			 Class<Repository> clazz = (Class<Repository>) Class.forName(packageName,false,loader);
			if(Repository.class.isAssignableFrom(clazz)){
				classes.add(clazz);
			}
		} catch (ClassNotFoundException e1) {}
	     
	     //是否循环迭代
	     boolean recursive = true;
	     
	     //获取包的名字 并进行替换
	     String packageDirName = packageName.replace('.', '/');
	     
	     //定义一个枚举的集合 并进行循环来处理这个目录下的things
	     Enumeration<URL> dirs;
	     try {
	         dirs = Thread.currentThread().getContextClassLoader().getResources(packageDirName);
	         //循环迭代下去
	         while (dirs.hasMoreElements()){
	             //获取下一个元素
	             URL url = dirs.nextElement();
	             //得到协议的名称
	             String protocol = url.getProtocol();
	             //如果是以文件的形式保存在服务器上
	             if ("file".equals(protocol)) {
	                 //获取包的物理路径
	                 String filePath = URLDecoder.decode(url.getFile(), "UTF-8");
	                 //以文件的方式扫描整个包下的文件 并添加到集合中
	                 findAndAddClassesInPackageByFile(packageName, filePath, recursive, classes);
	             } else if ("jar".equals(protocol)){
	                 //如果是jar包文件 
	                 //定义一个JarFile
	                 JarFile jar;
	                 try {
	                     //获取jar
	                     jar = ((JarURLConnection) url.openConnection()).getJarFile();
	                     //从此jar包 得到一个枚举类
	                     Enumeration<JarEntry> entries = jar.entries();
	                     //同样的进行循环迭代
	                     while (entries.hasMoreElements()) {
	                         //获取jar里的一个实体 可以是目录 和一些jar包里的其他文件 如META-INF等文件
	                         JarEntry entry = entries.nextElement();
	                         String name = entry.getName();
	                         //如果是以/开头的
	                         if (name.charAt(0) == '/') {
	                             //获取后面的字符串
	                             name = name.substring(1);
	                         }
	                         //如果前半部分和定义的包名相同
	                         if (name.startsWith(packageDirName)) {
	                             int idx = name.lastIndexOf('/');
	                             //如果以"/"结尾 是一个包
	                             if (idx != -1) {
	                                 //获取包名 把"/"替换成"."
	                                 packageName = name.substring(0, idx).replace('/', '.');
	                             }
	                             //如果可以迭代下去 并且是一个包
	                             if ((idx != -1) || recursive){
	                                 //如果是一个.class文件 而且不是目录
	                                 if (name.endsWith(".class") && !entry.isDirectory()) {
	                                     //去掉后面的".class" 获取真正的类名
	                                     String className = name.substring(packageName.length() + 1, name.length() - 6);
	                                     try {
	                                    	 Class<Repository> clsr = (Class<Repository>) Class.forName(packageName + '.' + className);
	                                    	 if(Repository.class.isAssignableFrom(clsr)){
		                                         //添加到classes
		                                         classes.add(clsr); 
	                                    	 }
	                                     } catch (ClassNotFoundException e) {
	                                    	 throw new RepositoryException(e);
	                                     }
	                                   }
	                             }
	                         }
	                     }
	                 } catch (IOException e) {
	                	 throw new RepositoryException(e);
	                 } 
	             }
	         }
	     } catch (IOException e) {
	        throw new RepositoryException(e);
	     }
	    
	     return classes;
	 }
	 
	 /**
	  * 以文件的形式来获取包下的所有Class
	  * @param packageName
	  * @param packagePath
	  * @param recursive
	  * @param classes
	  */
	 @SuppressWarnings("unchecked")
	private static void findAndAddClassesInPackageByFile(String packageName, String packagePath, final boolean recursive, List<Class<Repository>> classes){
	     //获取此包的目录 建立一个File
	     File dir = new File(packagePath);
	     //如果不存在或者 也不是目录就直接返回
	     if (!dir.exists() || !dir.isDirectory()) {
	         return;
	     }
	     
	     //如果存在 就获取包下的所有文件 包括目录
	     File[] dirfiles = dir.listFiles( file ->
	    	   //自定义过滤规则 如果可以循环(包含子目录) 或则是以.class结尾的文件(编译好的java类文件)
	           (recursive && file.isDirectory()) || (file.getName().endsWith(".class"))
	         );
	     
	     //循环所有文件
	     for (File file : dirfiles) {
	         //如果是目录 则继续扫描
	         if (file.isDirectory()) {
	             findAndAddClassesInPackageByFile(packageName + "." + file.getName(),
	                                   file.getAbsolutePath(),
	                                   recursive,
	                                   classes);
	         }
	         else {
	             //如果是java类文件 去掉后面的.class 只留下类名
	             String className = file.getName().substring(0, file.getName().length() - 6);
	             try {
	            	 Class<Repository> rcls = (Class<Repository>) Class.forName(packageName + '.' + className);
	            	 if(Repository.class.isAssignableFrom(rcls)){
		                 //添加到集合中去
		                 classes.add(rcls); 
	            	 }
	             } catch (ClassNotFoundException e) {
	            	 throw new RepositoryException(e);
	             }
	         }
	     }
	 }
}
